Abstract: With the purpose of solving the problems that come from the spread and application about coal chock carrier with a trailer，the design features of chock trailer are analyzed. And based on the advantage that the semi-trailer fifth wheel is compact, the three-axis hinge mechanism in chock trailer, which influences the service performance of chock carrier, is improved, and the vehicle parameters are optimized, and the underworkings adaptability of the vehicle is refined. Meanwhile, with the special road conditions in coal, the using features of the chock trailer fifth wheel is researched, and some rational maintaining measures are suggested, which assured the service life of the fifth wheel.